Drum type induction furnace



June 28, 1949. M. TAMA Erm..

DRUM TYPE INDUCTION FURNAGE 2 Sheets-Sheet 1 Filled Nov. 29, 19'47- June28, 1949. M. TAMA Erm.

DRUM TYPE INDUCTION FURNACE 2 lSheena-shear. 2

Filed Nov. 29, 1947 F'IG.5

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Patented June 28, 1949 2.474.443 DRUM TYPE INDUCTION FURNACE Mario Tama,Morrisville, Pa., and James Lloyd Hoff, Pennington, N. J., assignors toAjax Engineering Corporation, Trenton, N. J.

Application November 29, 1947, Serial No. 788,912

16 Claims. l

This invention is a further development of the drum-type inductionfurnace disclosed in pending U. S. application Ser. No. 771,360, filedAugust 29, 1947 and it relates particularly to the equipment for tiltinga drum-type induction furnace into its various operating positions.

The metal holding chamber or hearth of this induction furnace haspreferably a cylindrical shape. The furnace is equipped with threeinductor units or inductor unit rows and these inductor units areattached to the circumference of the .furnace casing below itshorizontal center plane. The inductor units contain in the usual mannera primary transformer assembly and a secondary melting loop, the latterbeing threaded by the transformer assembly and being connected with the-metal holding chamber or hearth of the furnace.

In the normal operating position the melting loop of one inductor unitor inductor unit row extends through the vertical center plane of thefurnace and the melting loops of the other inductor units or inductorunit rows are located laterally of the center inductor unit and extendthrough planes forming an acute angle with the vertical center plane ofthe furnace.

The invention is concerned with the important problem of rotating ortilting the furnace in its various operating positions while maintainingthe same in working order.

The here appertaining operational particularities of a drum-type furnaceof the present type are, as follows.

The furnace is to be rotated in three different positions for theemptying of a faulty inductor unit and its replacement and into afurther position for the total discharge o'f the metal; moreover, thecleaning of the melting ducts and the reorientation of certain parts ofthe rotating equipment necessitates the tilting of the furnace intocorresponding positions.

It is therefore the primary object of this invention to provide anequipment for rotating or tilting the furnace in three positions whichwill enable the emptying of the metal from the melting loop and thereplacement or removal of the faulty inductor unit.

It is a further object of the invention to provide a tilting `equipmentwhich renders it possible to keep during the removal of a faultyinductor unit a sufficient heel of metal in the furnace and in the otherinductor units and to assure during the replacement an uninterruptedworking of the furnace.

It is a further object of this invention to provide a tilting equipmentwhich enables the rotation of the furnace in a position for a totalremoval of the molten metal charge.

It is also an object of this invention to secure the furnace during itsrotative movement and in its operating positions.

It is a further object of the invention to simplify the exchange of theinductor units and to considerably shorten the time which is requiredfor their replacement. l

It is also an object of the invention to provid a tilting equipmentwhich will enable the furnace to be rotated in a position for the easycleaning of the melting channels.

It is another object of the invention to prevent the accumulation ofslag deposits in the melting channels of the inductor units and toeliminate the clogging thereof, thereby greatly reducing the necessityfor their replacement or exchange; in this respect the instant furnaceshows a decided improvement over the art, because it permits thecleaning of the melting channels from the outside of the furnace withoutinterrupting the melting while an inductor unit is being exchanged.

With'these and other objects in view which will become apparent asthisapplication proceeds, the tilting equipment of the instant drumtypefurnace will now be described in several preferred embodiments which areillustrated in the attached drawings. However, it is to be understoodthat the invention is not restricted to the modifications described andshown.

In the drawings,

Fig. 1 is a vertical sectional view of a drumtype furnace in accordancewith this invention taken in its longitudinal direction,

Fig. 2 ,is a vertical cross-sectional view taken on line 2 to 2 of Fig.1 showing the furnace in its normal working position,

Fig. 3 is a plan view of the right end side of the furnace,

Figs. 4, 5, 6 and 7 are plan views of the left end side of the furnaceshowing the furnace tilting equipment in various operating positions.

Fig. 4 shows this equipment in the normal operating position,

Fig. 5 shows it in the position for replacement of the left inductorunit,

Fig. 6 shows it in the position for the replacement of the rightinductor unit,

Fig. 7 shows it in the position for the replacement of the centerinductor unit,

Fig. 8 is a vertical scale-reduced sectional View similar to that ofFig. 2 of the furnace in the Fig. 9 is a similar vertical sectional viewof the furnace in the position for the replacement of the right inductorunit,

Fig. 10 is a similar vertical sectional view of the furnace in theposition for the replacement of the center inductor unit,

Figs. 11 to 1'7 are schematical views of the furnace tilting or rotatingmechanism in its various operating positions.

The furnace shown in the drawing is provided with a cylindrical casing Iwhich is protected by a refractory lining 2; the casing houses ahorizontal hearth or metal holding chamber 8; the casing has attached toits circumference three inductor units 4, 5 and 6. Rows of inductorunits may replace the single units.

The normal working position of the furnace corresponds to the one shownin Figures 2, 4, 11.

The furnace has a top opening which is closed by a removable cover 1.The furnace drum is provided at both ends with circular tracks 8 restingon Wheels 9 supported by roller bearings; the latter are mounted on basei; rollers 33 are provided to prevent the longitudinal displacement ofthe furnace drum.

The inductor units are so arranged that in the normal working positionof the furnace the melting loop of the center or bottom unit extendsthrough the Vertical center plane whereas the melting loops of thelateral inductor units 4 and 8 extend through planes which form acuteangles of preferably 50 with the vertical center plane.

The melting loops consist of a melting channel I2 which is spaced fromthe hearth 3 and preferabl-y extends parallel to the longitudinaldirection of the drum axis and three straight channels I3, i4, I5connecting channel I2 with hearth 3. The melting channels are in thecustomary manner threaded by the transformer units having coil windingsI6 of insulated copper wire and an iron core I1 closed toward the coilwindings. Cooling blowers I9 are attached to the inductor units; theyserve to remove the heat from the primary windings.

In view of the generally known arrangement of these inductor units amore detailed description thereof is not deemed to be required. Theunits are housed in refractory lined casings Il which are removablyattached to the drum casing I l in the manner shown in U. S. Patent2,423,912; the inductor units may be removed by loosening bolts, notshown, which connect the drum casing I with the ind-uctor casings Il.

The furnace may be filled in its normal operating position up to leveli8.

The inclination of the lateral inductor units 4, 6 may be preferablychosen in lsuch a manner that the center lines 24 of all meltingchannels located in the same vertical plane converge at a point 20located above the geometrical center 2| of the furnace. see Fig. 2. Inthe extension of the center lines 24 openings 22 are provided in thedrum cover through which cleaning tools may be introduced into themelting channels while the same are full with the molten metal. Aninclination of about 50 degrees of the lateral melting loops relative tothe center or bottom melting loop has proven to be particularlyadvantageous; the melting channels having this inclination can becleaned without emptying the furnace.

The important advantage of this furnace is the easy replacement ofworn-out inductor units without interrupting the working of the furnace;this is rendered possible by an equipment for rotating the `furnace intoits Various Operating 4 positions, which forms the subject matteiv oithis invention.

The exchange of an inductor unit is performed after rotating the furnaceto a position where the melting loop of the unit to be replaced hasreached' approximately the horizontal center plane of the furnace andthe molten metal has been discharged from its melting loop.

The metal is discharged from the drum over opening 5i connected with adischarge spout 30 made of cast iron and provided with a refractorylining 3|. By tilting the furnace, molten metal can be taken outgradually under full control of the pouring speed. 'Ihe furnace reachesits highest metal level I8 when in the position shown in Fig. 2. Fromthere on molten metal can be discharged over spout until the workinglimit is reached; further tilting would be of no avail. If additionalmetal is to be discharged another opening 50located in a sidewall of thefurnace has to be used, which opening is ordinarily closed by arefractory plug.

A door 32 is provided which facilitates the removal of slags from thesurface of the bath. One or more of the cover sections should be removedbefore the slags are pushed-out through this door opening.

The rotation of the furnace into its operating positions and theequipment for performing this work will now be described in detail.

The furnace drum is, as already mentioned, rotatably mounted on base i0by means of circular tracks 8 which are supported on rollers 9.

Three notches 44, 45, 46 are attached to the left sidewall of thefurnace casing I; notches 44. 45 open out towards the center of the drumand notch 48 opens out in an opposite direction. A small hydrauliccylinder 4i is fastened to arm 40 of lever 21; a second hydrauliccylinder 28 is mounted on base i0.

The rotation of the furnace casing is effected by the hydraulic cylinder28, its ram 26 and rotatable double arm lever 21 which may be mounted ina suitable bearing located in the center of the furnace casing; the twoarms of this lever may be inclined relative to each other at an angle of134. Cylinder 23 is rotatably mounted on base Ill by means of lugs 25and a. pin 29.

'I'he normal operating position of the furnace is shown in Figs. 2, 4,12.

The ram of hydraulic cylinder 28 is kept out of engagement with notch48; the furnace casing is operatively coupled with lever 21 byengagement of the ram of cylinder 4I with notch 44.

The melting duct of inductor unit 5 is positioned in the vertical centerplane of the furnace; the melting ducts of inductor units 4 and 6 areinclined at an angle of about 50 relative to this vertical center plane.

In order to replace inductor unit 4 the furnace is clockwise tilted inthe position which is shown in Figs. 5, 8, 12. For this purpose the ramof hydraulic cylinder 28 is retracted, lever 21 is in engagement withnotch 44. The melting duct of inductor unit 4 is in this positionslightly above the horizontal center plane of the furnace and slopesdown thus allowing the metal to be emptied from the inductor unit intothe furnace hearth. Since the hole 50 is below the level of the inductorunit the metal level in the furnace is also below the inductor unit. Inthis position the inductor may :be changed without spilling metal whilekeeping enough metal in the drum to keep the two units 5 and 5 operativewhile the inductor 5. unit I is being changed. Further, there issufflcient metal in the drum to fill the new unit when the furnace isreturned to the normal position of Figs. 2 or 4. Hence, it is possibleto change inductor I withoutl spilling metal and without the necessityof adding molten metal to the furnace for the starting of the newinductor unit. Inductor units and 6 continue to operate and serve tomaintain the temperature of the metal left in the drum while a faultyunit 4 is being replaced.

For the exchange of inductor unit l6 the furnace must be rotated in acounterclockwise manner in the position shown in Figs. 6, 9, 13.

In this position the conditions concerning the molten charge are thesame as in the position shown in Fig. 5 except that the hole 50 is nowabove the level of the inductor. Hence, when replacing unit t it isnecessary to first pour out sufficient metal from the furnace to lowerthe metal level to that shown in Fig. '9.

The change of the center inductor unit 5. is more difficult; however,the position shown in Figs. 7, 1-0, 15 satisfies these requirements.

Upon draining this unit there is sufficient metal in the drum for theoper-ation of inductor unit 6. Depending upon the physical size andproportions of the furnace, inductor unit 5 may or may not be filled bythe metal remaining in the drum. However, solid metal may be added tothe furnace and melted by unit 6 until sufficient metal is in thefurnace to o'od unit 5 and get it into operation.

In the following the sequence of the furnace operations for changing theinductor units and for emptying the metal from the same and from thefurnace will now be described with reference to Figs. ll to 17.

lit should be noted that the angie Ibetween the inductor units is chosento be 50. `The directions along which arm fill of lever 2l extends inits various operating positions are indicated by a and since, as laterexplained, a change of the position of lever 2l mustbe executed for theinstallment of certain operating positions. The inductor units are alsohere indicated by numerals 4, 5 and ii.

Fig. 11 indicates the normal working position of the furnace also shownon Figs. 2 and 4.

Cylinder 23 has its ram retracted and, therefore, does not inuence theoperation of the equipment. Cylinder 3i attached to the one end of armfill has its ram extended to engage notch di. Lever 2l is thus locked tothe drum and cylinder 23 may be used to rotate the furnace, if

desired, in either towards a.

If cylinder 23 is operated to turn arm 4@ of lever 2l for 38 degress ina clockwise direction the position of Fig. l2 is reached for thereplacement of inductor unit 4. Arm 4G still locked in notch 44 pointstowards a; the ram of cylinder 28 remains unlocked from notch d6. By thedownward slope of the melting loop towards the hearth, see Fig. 8, themetal can be emptied from the loop before the replacement of theinductor unit is undertaken. By this clockwise rotation also the spoutopening has been lowered delivering metal from the furnace.

By a counterclockwise rotation from the initial position of Figs. l1, 2,4 through an angle of 49 the furnace arrives in the position shown inFig. 13 which position is also shown in Figs. 6 and 9. This is theposition for the exchange of inductor unit 6. Cylinder 28 is stillunlocked.

direction. Arm di] points This rotation also raises opening 50 andallows metal to lbe charged into the furnace without overflowing intothe spout; in this position inductor unit y6 has a slope towards thehearth 0f 2/2.

In order to change inductor unit 5 the furnace is first brought into theposition of Fig. l2, whereby notch 46 appears on top of cylinder 28; theram of this cylinder is actuated and engages the notch. The ram of smallcylinder 4I is retracted from notch 44 and lever 21 is now free fromengagement with the drum. The drum is stopped from moving by the ram ofcylinder 28. In this position the ram 26 may be retracted. The lever 21is now rotated in a counterclockwise direction into the position of Fig.14, where the ram of cylinder 4i on arm 4l) may now be used to engagenotch 45 and the arm I4ll points towards The ram of cylinder 28 is nowretracted from notch 46. The drum is again capable of being rotated bylever 21 and ram 26. The ram 26 is now extended and the furnace isrotated in a clockwise direction. If the rotation is stopped at 49 fromposition of Fig. 2 or 5, the position of Fig. 15 is reached and theinductor unit 5 is now on the left of the vertical center line and willhave a downward slope of 21/2o towards the center of the furnace. Thisis sufficient to drain it of molten metal and thus allow it to beremoved.

If the rotation is continue-d as far as possible this will ybringinductor unit i5 in the position of Fig. 16 and slightly above thehorizontal center line. In this position all inductors are empty and thefurnace is drained completely.

To return the furnace into its normal position of Fig. 1l or 4 ram 2liis fully retracted, the drum is locked by the ram of cylinder 28engaging notch d6. ram of cylinder di is retracted freeing arm 2l; ram2c is extended, the ram of cylinder il is engaged in notch @ill andcylinder 28 is disconnected releasing the furnace drum. The furnace isin the position of Fig, 12 and is easily returned to the normaloperating position of Figs. l1 or 4.

The equipment for rotating or tilting the instant drum-type furnace inits various operating positions is described and shown in thespeciilcation and drawings by way of example only and the equipment aswell as its various parts may be replaced by equivalent means withoutdeparting from the spirit of this invention as recited in the appendedclaims.

What we claim is:

l. fn a drum-type induction furnace for molten metals a base, a metalholding chamber, a refractory lined casing housing said chamber,inductor units attached to the circumference of said casing below itshorizontal center plane, a secondary melting loop in said inductor unitsconnected with said molten metal holding chamber. the melting loop ofone of said inductor units extending through a vertical center plane ofthe furnace and the-melting loops of the other lateral inductor unitsextending through a plane forming an acute angle with said verticalcenter plane, means to rotatably support the furnace and to rotate thesame into its operating positions.

2. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamloer, a refractory lined cylindricalcasing housing said chamber, inductor units attached to the'circumferenc'e of said casing below its horizontal center plane, asecondary melting loop in said inductor units connected with said moltenmetal holding chamber, the melting loop of one of said 7 inductor unitsextending through a vertical center plane of the furnace and the meltingloops of the other lateral inductor units extending through a planeforming an acute angle with said vertical center plane, means supportedon said base and means attached to said casing to rotatably support thefurnace and means supported on said base and connected with said casingto rotate the furnace into its operating positions..

' 3. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, a refractory lined cylindrical casinghousing said chamber, inductor units attached to the circumference ofsaid casing below its horizontal center plane, a secondary melting loopin said inductor units connected with said molten metal holding chamber,the melting loop of one of said inductor units extending through avertical center plane of the furnace and the melting loops of the otherlateral inductor units extending through a plane forming an acute anglewith said vertical center plane, circular tracks attached to thecircumference of said casing and rollers on said base to rotatablysupport said tracks and means supported on said base and connected withsaid casing to rotate the furnace in three positions for the exchange ofthe inductor units and in a position for the total discharge of themolten metal.

4. In a drum-type induction furnace for molten metals a base, acylindrical metal holding charnber, a refractory lined cylindricalcasing housing said chamber, inductor units attached to thecircumference of said casing below its horizontal center plane, asecondary melting loop in said inductor units connected with said moltenmetal holding chamber, the melting loop of one of said inductor unitsextending through a vertical center plane of the furnace and the meltingloops of the other lateral inductor units extending through a planeforming an acute angle with said vertical center plane, means torotatably support the furnace and means to rotate the same in itsoperating positions said means including a hydraulic cylinder rotatablysupported on said base, a ram in said cylinder, at least two notchesprovided at the circumference of said casing and means for effecting theoperative engagement of the cylinder ram with said notches.

5. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, a refractory lined cylindrical casinghousing said chamber, inductor units attached to the circumference ofsaid casing below its horizontal center plane, a secondary melting loopin said inductor units connected with said molten metal holding chamber,the melting loop of one of said inductor units extending through avertical center plane of the furnace and the melting loops of the otherlateral inductor units extending through a plane forming an acute anglewith said vertical center plane,'means to rotatably support the furnaceon said base and means to rotate the furnace in its operating positionssaid means including a hydraulic cylinder rotatably mounted on saidbase, a ram in said cylinder, at least two notches provided at thecircumference of said casing, a double arm lever rotatably carried onsaid casing, the end of the one arm being rotatably connected with theram of said hydraulic cylinder and a hydraulic ram attached to the endof the 4second arm for engagement with said notches.

6. In a furnace according to claim 5 the angle of inclination betweentwo adjacent inductor units being about 50 and the arms of the doublearm lever enclosing therebetween an angle of about 134.

7. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, a refractory lined cylindrical casinghousing said chamber, inductor-units attached to the circumference ofsaid casing below its horizontal center plane, a secondary melting loopin said inductor units connected with said molten metal holding chamber,the melting loop of one oi said inductor units extending through avertical center plane of the furnace and the melting loops of the otherlateral inductor units extending through a plane forming an acute anglewith said vertical center plane, means to rotatably support the furnaceon said base and means to rotate the furnace in its operating positions,said means including a hydraulic cylinder rotatably mounted on saidbase, two notches provided at the circumference of said casing, a doublearm lever rotatably carried in the center of said casing, one of saidarms being rotatably connected with the ram of said hydraulic cylinderand means to effect the engagement of the second lever arm with eitherone of said two notches.

8. In a furnace according to claim 7 means to hold the furnace casing ina fixed position during the change of engagement of the second lever armfrom one to the second notch.

9. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, a refractory lined cylindrical casinghousing said chamber, inductor units attached to the circumference ofsaid casing below its horizontal center plane, a secondary melting loopin said inductor units connected with said molten metal holding chamber,the melting loop of one of said inductor units extending through avertical center plane of the furnace and the melting loops of the otherlateral inductor units extending through a plane forming an acute anglewith said vertical center plane, means to rotatably support the furnaceon said base, means to rotate the furnace in its operating positionssaid means including a hydraulic cylinder, a ram in said cylinder meansto rotatably support the one end of said cylinder on said base, threenotches provided at the circumference of said casing, means to effectthe engagement of said ram in either of two of said notches, a doublearm lever rotatably carried in the center of said casing, one lever armbeing connected with said ram, a ram attached to the second lever armfor engagement with said two notches and a ram 1ocated on said base forengagement with said third notch to hold the furnace casing in a fixedposition during the change of engagement of said lever with one to theother of said two notches.

10. In a drum-type induction furnace for molten metals a base, a metalholding chamber, a refractory lined casing housing said chamber,inductor unit rows attached to the circumference of said casing belowits horizontal center plane, a secondary melting loop in said inductorunits connected with said molten metal holding chamber, the meltingloops of the inductor units of the center row extending through avertical center plane of the furnace and the melting loops of theinductor units of the lateral rows extending through a plane forming anacute angle with said vertical center plane, means to rotatably supportthe furnace and to rotate the same into its operating positions.

il. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, a refractory lined cylindrical casinghousing said chamber, inductor unit rows attached to the circumferenceof said casing below its horizontal center plane, a secondary meltingloop in said inductor units connected with said molten metal holdingchamber, the melting loops of the inductor vunits of the center rowextending through a ve-tical center plane of the furnace and the meltingloops of the inductor units of the lateral rows extending through aplane forming an acute angle with said vertical center plane, meanssupported on said base and means attached to said casing to rotatablysupport the furnace and means supported on said liaise and connectedwith said casing to rotate `the furnace into its operating positions.

12. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, a refractory lined cylindrical casinghousing said chamber, inductor unit rows at tached to the circumferenceof said casing below its horizontal center plane, a secondary meltingloop in said inductor units connected with said molten metal holdingchamber, the melting loop of the inductor units of the center rowextending through a vertical center plane of the furnace and the meltingloops of the inductor units of the lateral rows extending through aplane forming an acute angle with said vertical center plane, circulartracks attached to the circumference ofA said casing and rollers on saidbase to rotatably support said tracks and means supported on said baseand connected with said casing to rotate the furnace in three positionsfor the exchange of the inductor units and in a position for the totaldischarge of the molten metal.

13. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, inductor unit rows attached to thecircumference of said casing below its horizontal center plane, asecondary melting loop in said inductor units connected with said moltenmetal holding chamber, the melting loops of the inductor unit of thecenter row extending through a vertical center plane of the furnace andthe melting loops of the inductor units of the lateral rows extendingthrough a plane forming an acute angle with said vertical center plane,means to rotatably support the furnace and means to rotate the same inits operating positions said means including a hydraulic cylinderrotatably l supported on said base, a ram in said cylinder, at

least two notches provided at the circumference of said casing and meansfor effecting the operative engagement of the cylinder ram with saidnotches.

14. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, a refractory lined cylindrical casinghousing said chamber, inductor unit rows attached to the circumferenceof said casing below its horizontal center plane,V a secondary meltingloop in said inductor units connected with said molten metal holdingchamber, the melting loops of the inductor units of the center rowextending through a vertical center plane of the furnace and the meltingloops of the inductor units of the lateral rows extending through aplane forming an acute angle with said vertical center plane, means torotatably support the furnace on said base and means to rotate thefurnace in its operating positions said means including a hydrauliccylinder rotatably mounted on said base, a ram in said cylinder, atleast two notches provided at the circumference of said casing, a doublearm lever rotatably carried on said casing, the end of the one arm beingrotatably connected with the ram of said hydraulic cylinder and ahydraulic ram attached to the end of the second arm for engagement withsaid notches.

15. In a drum-type induction furnace for molten metals a base, acylindrical metal holding chamber, a refractory lined cylindrical casinghousing said chamber, inductor unit rows attached to the circumferenceof said casing below its horizontal center plane, a secondary meltingloop in the said inductor units connected with said molten metal holdingchamber, the melting loops of the inductor units of the center rowextending through a vertical center plane of the furnace and the meltingloops of the inductor units of the lateral rows extending through aplane forming an acute angle with said vertical center plane, means torotatably support the furnace on said base and means to rotate thefurnace in its operating positions, said means including a hydrauliccylinder rotatably mounted on said base, two notches provided at thecircumference of said casing, a double arm lever rotatably carried inthe center of said casing, one of said arms being rotatably connectedwith the ram of said hydraulic cylinder and means to effect theengagement of `the second lever arm with either one of said two housingsaid chamber, inductor unit rows attached to the circumference of saidcasing below its horizontal center plane, a secondary melting loop insaid inductor units connected with said molten metal holding chamber,the melting loop of the inductor units of the center row extendingthrough a vertical center plane of the furnace and the melting loops ofthe inductor units of the lateral rows extending through a plane formingan acute angle with said vertical center plane, means to rotatablysupport the furnace on said base, means to rotate the furnace in itsoperating positions said means including a hydraulic cylinder, a ram'insaid cylinder, means to rotatably support the one end of said cylinderon said base, three notches provided at the circumference of saidcasing, means to effect the engagement of said ram with either of two ofsaid notches, a double arm lever rotatably carried in the center of saidcasing, one lever arm being connected with said ram, a ram attached tothe second lever arm for engagement with said two notches and a ramlocated on said base for engagement with said third notch to hold thefur-v nace casing in a xed position during the change of engagement ofsaid lever with one to the other of said two notches. k

MARIO TAMA. JAMES LLOYD HOFF.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATNTS Number Name Date 1,069,923 Crafts Aug. 12, 19131,201,671 Wyatt Oct. 17, 1916 2,102,582 Summey Dec. 14, 1937 2,423,912Tama et al 1-- July 15, 1947

